Induced and spontaneous abortion and incidence of breast cancer among young women - A prospective cohort study

Department of Nutrition , Harvard University, Cambridge, Massachusetts, United States
Archives of Internal Medicine (Impact Factor: 17.33). 05/2007; 167(8):814-20. DOI: 10.1001/archinte.167.8.814
Source: PubMed


Induced abortion has been inconsistently associated with breast cancer risk in case-control studies. Retrospective cohort studies using registry information in Scandinavia have not suggested an increase in the incidence of breast cancer, although data on individual reproductive factors were not accounted for.
We examined the association between induced and spontaneous abortion and the incidence of breast cancer in a prospective cohort of young women, the Nurses' Health Study II. The study included 105 716 women 29 to 46 years old at the start of follow-up in 1993. Information on induced or spontaneous abortions was collected in 1993 and updated biennially. During 973 437 person-years of follow-up between 1993 and 2003, 1458 newly diagnosed cases of invasive breast cancer were ascertained.
A total of 16 118 participants (15%) reported a history of induced abortion, and 21 753 (21%) reported a history of spontaneous abortions. The hazard ratio for breast cancer among women who had 1 or more induced abortions was 1.01 (95% confidence interval, 0.88-1.17) after adjustment for established breast cancer risk factors; among women with 1 or more spontaneous abortions, the covariate-adjusted hazard ratio was 0.89 (95% confidence interval, 0.78-1.01). The relation between induced abortion and the incidence of breast cancer did not differ materially by number of abortions (P for trend = .98), age at abortion (P for trend = .68), parity (P for interaction = .54), or timing of abortion with respect to a full-term pregnancy (P for interaction = .10).
Among this predominantly premenopausal population, neither induced nor spontaneous abortion was associated with the incidence of breast cancer.

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    • "Harvesting must occur before beginning cytotoxic chemotherapy and women should be referred for fertility evaluation at the time of diagnosis. Use of tamoxifen or letrozole for ovarian stimulation might be safer approaches [75]. Young women undergoing breastconserving therapy can have a higher rate of local recurrence than older women, and this issue should be specifically addressed in preoperative counseling of these women. "

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    • "Subtotal (I-squared = 76.6%, p < 0.001) Paoletti (2003) Palmer (2004b) Reeves (2006) Andrieu (2006) Subtotal (I-squared = 0.0%, p = 0.569) Tang (2000) Brauner (2013) Michels (2007) Incidence "
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    ABSTRACT: Although positive association between abortion and breast cancer was frequently reported from case-control studies, results from prospective studies were still unclear. This study aimed to evaluate this association based on prospective studies. PubMed, ISI Web of Knowledge and Embase were systematically searched for prospective studies on the association between abortion and breast cancer up to April 2014, supplemented by manual searches on the references. Two reviewers independently conducted the literature search, study selection, data extraction, and quality assessment of included studies. Random effects models were used to estimate the combined relative risks (RRs) and corresponding 95 % confidence intervals (95 % CIs). Fifteen prospective studies [14 focused on induced abortion (IA), and 12 focused on spontaneous abortion (SA)] were included in the final analysis. The combined RRs (95 % CIs) of breast cancer risk were 1.00 (0.94-1.05) [1.00 (0.92-1.08) for cumulative-incidence data and 1.00 (0.94-1.05) for incidence-rate data] for IA, and 1.02 (0.95-1.09) [1.06 (0.96-1.16) for cumulative-incidence data and 1.01 (0.92-1.09) for incidence-rate data] for SA, respectively. Non-significant associations of breast cancer with IA and SA were also found among nulliparous women, women with abortion before or after the first full-term pregnancy, women with one or ≥2 abortions, and women with first abortion after 30 years old. The current prospective evidences are not sufficient to support the positive association between abortion (including IA and SA) and breast cancer risk.
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    • "In the present study, the multiple analyses showed that the use of the pills does not increase the odds of breast cancer incidence, but it in fact decreases the odds. Experienced based studies strongly suggest that estrogen plays an important role in not only the incidence of the cancer but also its development stages.[16] Considering the benefits of the OCPs, further studies on specific groups of cancer patients should be conducted in order to identify the true role of this factor in the incidence of breast cancer. "
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    ABSTRACT: Background: Breast cancer is the most prevalent type of cancer among Iranian females; it is noteworthy that the condition of this type of cancer among Iranian women does not significantly differ from what has been reported from other countries. Considering the importance of this issue, identification of the backgrounds factors and risk factors of the breast cancer risk are highly needed. Therefore, the present study is aimed to compare the risk factors of resident patients of Isfahan province, Iran, with accredited risk factors by other countries and also identify the importance of each factor in the incidence of cancer. Materials and Methods: The present work is a case-control study, which was conducted in 2011. In order to conduct the study, 216 women who had been clinically identified with breast cancer were selected from Seiedo-Shohada Hospital, Isfahan, Iran, as the case group. Moreover, 41 healthy women who were the relatives of the selected patients (i.e., sisters and aunts) were selected as the control group. The data and information of the patients from 1999 to 2010 were collected from either assessing the database system of the center for breast cancer research or interviewing the patients through phone. To analyze the data, multiple logistic regression method was applied. Results: The range of age among selected individuals in this study was from 20-75 years old. The determinant factors for odds of breast cancer included in the applied multiple logistic regression model were the use of oral contraceptive pills (OCPs) (odds ratio [OR] =0.18, 95% confidence interval [CI] = 0.04-0.75) as the protective factor, hormone replacement therapy (OR = 10.2, 95% CI = 1.18-88.89) and menopause at old age (OR = 1.26, 95% CI = 1.11-2.12) as the risk factors. Furthermore, there was not seen any significant relationship between age, vocation, and marital status with odds of breast cancer in multiple model. Conclusion: Based on the results, use of OCPs as protective factor, hormone replacement therapy, and menopause at old age are identified as the risk factors in developing breast cancer among women. Influencing and modifiable factors should be considered very important in society based interventions and preventive interventions planning.
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